Improved writing-fluid



UNITED STATES HENRY C. BAILDON, OF EDINBURGH, SCOTLAND.

IMPROVED WRITING-FLUID.

Specification forming part of Letters Patent No. 49,843, dated September 5, 1865.

To all whom it may concern.-

Be it known that I, HENRY O. BAILDON, of Edinburgh, Scotland, have invented a new and useful Improvement in the Manufacture of WVriting-Fluids; and I do hereby declare that the following is a full,clear, and exact description thereof, which will enable others skilled in the art to fully understand and make use of the same.

The object of this invention is the prevention of fraudulent alterations in bankers drafts, notes, checks, and other documents in which it is important to avoid alteration and erasure.

The invention consists in the use of an ink or writing-fluid composed of an acid and coloring-matter that can be combined therewith, to be used in combination with a paper the color in which may be discharged or changed by such acid, and the texture of the paper also changed or weakened by the action thereof in those parts that are written upon, and the possibility of alteration and erasure is pre- "ented.

The ink or writing-fluid. above referred to is or may be composed of diluted sulphuric acid and indigo-paste, as a coloring-matter, in the proportion of a qnarter of an ounce of indigopaste to three-quarters of an ounce of sulphuric acid; but I prefer adding to the indigopaste a small proportion of magenta crystal or other aniline coloring-matter 5 and the paper intended to be used is blue-tinted paper, or paper tinted or colored with any coloringmatter which will be acted upon by the acid, so as to discharge or change the color at the back of the paper and weaken the texture of the paper.

The paper used, by preference, is a paper tinted or colored with ultramarine, which may be of a deeper tint than usual; butpaper colored green or with any other color may also be used.

The above proportion of acid and coloringmatter used with the composition of the ink or writing-fluid may be varied to suit different kinds of paper-thatis to say, the strength of the acid used with the indigo-paste or sulphate of indigo used in preparing theink may be increased or diminished, according to the texture of the paper to be acted upon, and other acids besides sulphuric acid maybe employed for the purpose.

I do not claim as my invention the use of an ink or writing-fluid for only discharging color from paper, such having been used long ago; but

I claim as new and desire to secure by Letters Pa tent The use for the purpose described of paper tinted or colored with a coloring-matter susceptible of being acted upon by sulphuric or other destructive acid, combined with the use of an ink composed of sulphuric or other (lestructive acid and a coloring-matter, suchink being capable of discharging and changing the color of the paper and changing or weakening the texture thereof in the parts written upon, substantially as herein set forth.

HENRY O. BAILDON.

Witnesses:

J AllTES HUNTER, GEO. Ross. 

